Extreme ultraviolet mask and method for forming the same

ABSTRACT

A photolithography mask includes a substrate, a reflective multilayer structure over the substrate, an adhesion layer over the reflective multilayer structure, a capping layer over the adhesion layer, and a patterned absorber layer over the capping layer. The capping layer includes a non-crystalline conductive material.

PRIORITY CLAIM AND CROSS-REFERENCE

This application is continuation of U.S. patent application Ser. No.16/889,604, filed Jun. 1, 2020, which claims the benefit of U.S.Provisional Patent Application No. 62/893,753, filed Aug. 29, 2019,which applications are incorporated by reference herein in theirentireties.

BACKGROUND

The semiconductor industry has experienced exponential growth.Technological advances in materials and design have produced generationsof integrated circuits (ICs), where each generation has smaller and morecomplex circuits than the previous generation. In the course of ICevolution, functional density (i.e., the number of interconnecteddevices per chip area) has generally increased while geometry size(i.e., the smallest component or line that can be created using afabrication process) has decreased. This scaling down process generallyprovides benefits by increasing production efficiency and loweringassociated costs.

BRIEF DESCRIPTION OF THE DRAWINGS

Aspects of the present disclosure are best understood from the followingdetailed description when read with the accompanying figures. It isnoted that, in accordance with the standard practice in the industry,various features are not drawn to scale. In fact, the dimensions of thevarious features may be arbitrarily increased or reduced for clarity ofdiscussion.

FIG. 1 is a cross-sectional view of an extreme ultraviolet (EUV) mask,in accordance with some embodiments.

FIG. 2 is a flowchart of a method for fabricating an EUV mask, inaccordance with some embodiments.

FIGS. 3A-3H are cross-sectional views of an EUV mask at various stagesof a fabrication process, in accordance with some embodiments.

DETAILED DESCRIPTION

The following disclosure provides many different embodiments, orexamples, for implementing different features of the provided subjectmatter. Specific examples of components and arrangements are describedbelow to simplify the present disclosure. These are, of course, merelyexamples and are not intended to be limiting. For example, the formationof a first feature over or on a second feature in the description thatfollows may include embodiments in which the first and second featuresare formed in direct contact, and may also include embodiments in whichadditional features may be formed between the first and second features,such that the first and second features may not be in direct contact. Inaddition, the present disclosure may repeat reference numerals and/orletters in the various examples. This repetition is for the purpose ofsimplicity and clarity and does not in itself dictate a relationshipbetween the various embodiments and/or configurations discussed.

Further, spatially relative terms, such as “beneath,” “below,” “lower,”“above,” “upper” and the like, may be used herein for ease ofdescription to describe one element or feature's relationship to anotherelement(s) or feature(s) as illustrated in the figures. The spatiallyrelative terms are intended to encompass different orientations of thedevice in use or operation in addition to the orientation depicted inthe figures. The apparatus may be otherwise oriented (rotated 90 degreesor at other orientations) and the spatially relative descriptors usedherein may likewise be interpreted accordingly.

In the manufacture of integrated circuits (ICs), patterns representingdifferent layers of the ICs are fabricated using a series of reusablephotomasks (also referred to herein as photolithography masks or masks)in order to transfer the design of each layer of the ICs onto asemiconductor substrate during the semiconductor device fabricationprocess. Thus, any defects in the mask may be transferred to the ICs,potentially severely affecting the device performance. Defects that aresevere enough may render the mask completely useless, which increasesthe cost and production time.

With the shrinkage in IC size, extreme ultraviolet (EUV) light with awavelength of 13.5 nm is employed in, for example, a lithographicprocess to enable transfer of very small patterns (e.g., nanometer-scalepatterns) from a mask to a semiconductor wafer. Because most materialsare highly absorbing at the wavelength of 13.5 nm, EUV lithographyutilizes a reflective-type mask which selectively reflects and absorbsEUV radiation. A pattern formed on an EUV mask is transferred to asemiconductor wafer by reflecting EUV light off portions of a reflectivesurface of the EUV mask. It is important that the EUV mask must be asdefect free as possible because the lithography patterning is moresensitive to the mask defects for small feature sizes in the advancedtechnology nodes.

In some embodiments, a reflective-type EUV mask includes a masksubstrate, a reflective multilayer structure comprising alternativelystacked molybdenum (Mo) layers and silicon (Si) layers over the masksubstrate, and a patterned absorber layer over the reflective multilayerstructure. A ruthenium (Ru) capping layer is disposed over thereflective multilayer structure to prevent oxidation of the top Si layerin the reflective multilayer structure. However, during deposition of Ruonto the reflective multilayer structure, Ru metal tends to crystalizeon the surface of the top Si layer and/or intermix with Si at theinterface of the Ru capping layer and the top Si layer, resulting in anon-continuous coverage of the Ru capping layer on the top Si layer. Thenon-continuous Ru capping layer leads to degraded critical dimension(CD) uniformity when the EUV mask is used in the IC fabrication, whichin turn reduces the performance of ICs. Additionally, carbon from themetal organic precursor residues in the EUV exposure tool may diffuseinto the Ru capping layer and accumulate in the surface portion of theRu capping layer. Over time, the carbon contaminants result in asignificant reflectivity drop of the EUV mask, which adversely affectsthe performance of the EUV mask.

In embodiments of the present disclosure, an EUV mask with improvedquality and stability is provided. The EUV mask includes a substrate, areflective multilayer (ML) structure over the substrate, an adhesionlayer over the reflective ML structure, a Ru-based capping layer overthe adhesion layer, a patterned absorber layer over the capping layer,and a patterned anti-reflection layer over the patterned absorber layer.The adhesion layer introduced between the reflective multilayerstructure and the Ru-based capping layer helps to prevent thecrystallization of Ru when Ru is deposited onto the reflectivemultilayer structure. As a result, a capping layer with a continuouscoverage across the reflective multilayer structure is able to beobtained. The adhesion layer also helps to prevent Ru—Si intermixingduring the use of the EUV mask, thereby helping to improve stability ofthe EUV mask. In some embodiments, the Ru-based capping layer is furtherdoped with dopants with lower carbon solubility than Ru. As a result,the accumulation of carbon in the surface portion of the Ru-basedcapping layer is reduced during the use of the EUV mask, which leads tofurther increase the stability of the EUV mask.

FIG. 1 is a cross-sectional view of an EUV mask 100, in accordance withsome embodiments of the present disclosure. Referring to FIG. 1 , theEUV mask 100 includes a substrate 102, a reflective multilayer structure110 over a front surface of the substrate 102, an adhesion layer 112over the reflective multilayer structure 110, a capping layer 114 overthe adhesion layer 112, a patterned absorber layer 116P over the cappinglayer 114, and a patterned anti-reflection layer 118P over the patternedabsorber layer 116P. The EUV mask 100 further includes a conductivelayer 104 over a back surface of the substrate 102 opposite the frontsurface.

The patterned absorber layer 116P and the patterned anti-reflectionlayer 118P contain a pattern of openings 122 that correspond to circuitpatterns to be formed on a semiconductor wafer. The pattern of openings122 is located in a pattern region 100A of the EUV mask 100, exposing asurface of the capping layer 114. The pattern region 100A is surroundedby a peripheral region 100B of the EUV mask 100. The peripheral region100B corresponds to a non-patterned region of the EUV mask 100 that isnot used in an exposing process during IC fabrication. In someembodiments, the pattern region 100A of EUV mask 100 is located at acentral region of the substrate 102, and the peripheral region 100B islocated at an edge portion of the substrate 102. The pattern region 100Ais separated from the peripheral region 100B by trenches 124. Thetrenches 124 extend through the patterned anti-reflection layer 118P,the patterned absorber layer 116P, the capping layer 114, the adhesionlayer 112, and the reflective multilayer stack 110, exposing the frontsurfaced of the substrate 102.

In the present disclosure, by introducing an adhesion layer 112 betweenthe capping layer 114 and the reflective multilayer structure 110 toenhance the uniformity of the capping layer 114 and to reduce the carbonaccumulation during the use of the EUV mask 100, the quality and thestability of the EUV mask 100 are enhanced.

FIG. 2 is a flowchart of a method 200 for fabricating an EUV mask, forexample, EUV mask 100, in accordance with some embodiments. FIG. 3Athrough FIG. 3H are cross-sectional views of the EUV mask 100 at variousstages of the fabrication process, in accordance with some embodiments.The method 200 is discussed in detail below, with reference to the EUVmask 100. In some embodiments, additional operations are performedbefore, during, and/or after the method 200, or some of the operationsdescribed are replaced and/or eliminated. In some embodiments, some ofthe features described below are replaced or eliminated. One of ordinaryskill in the art would understand that although some embodiments arediscussed with operations performed in a particular order, theseoperations may be performed in another logical order.

Referring to FIGS. 2 and 3A, the method 200 includes operation 202, inwhich a hard mask layer 130 and a photoresist layer 140 are sequentiallyformed over an EUV mask blank 120, in accordance with some embodiments.In some embodiments, the EUV mask blank 120 includes, from bottom totop, a substrate 102, a reflective multilayer structure 110, an adhesionlayer 112, a capping layer 114, an absorber layer 116, and ananti-reflection layer 118.

The substrate 102 includes a material with a low thermal expansioncoefficient. The low thermal expansion material helps to minimize imagedistortion due to mask heating during use of the EUV mask 100. In someembodiments, the substrate 102 includes fused silica, fused quartz,calcium fluoride, silicon carbide, black diamond, titanium oxide dopedsilicon oxide (SiO₂/TiO₂), or other suitable low thermal expansionmaterials. In some embodiments, the substrate 102 has a thicknessranging from about 1 mm to about 7 mm. If the thickness of the substrate102 is too small, a risk of breakage or warping of the EUV mask 100increases, in some instances. On the other hand, if the thickness of thesubstrate is too great, a weight of the EUV mask 100 is needlesslyincreased, in some instances.

In some embodiments, a conductive layer 104 is disposed on a backsurface of the substrate 102. In some embodiments, the conductive layer104 is in direct contact with the back surface of the substrate 102. Theconductive layer 104 is operable to provide for electrostaticallycoupling of the EUV mask 100 to an electrostatic mask chuck (not shown)during fabrication and use of the EUV mask 100. In some embodiments, theconductive layer 104 includes chromium nitride (CrN). In someembodiments, the conductive layer 104 is formed by a deposition processsuch as, for example, chemical vapor deposition (CVD), plasma-enhancedchemical vapor deposition (PECVD), or physical vapor deposition (PVD).The thickness of the conductive layer 104 is controlled such that theconductive layer 104 is optically transparent.

The reflective multilayer structure 110 is disposed over a front surfaceof the substrate 102 opposite the back surface. In some embodiments, thereflective multilayer structure is in directly contact with the frontsurface of the substrate 102. The reflective multilayer structure 110provides a high reflectivity to the EUV light. In some embodiments, thereflective multilayer structure 110 is configured to achieve about 60%to about 75% reflectivity at the peak EUV illumination wavelength. Insome embodiments, the reflective multilayer structure 110 includesalternatively stacked layers of a high refractive index material and alow refractive index material. A material having a high refractive indexhas a tendency to scatter EUV light and on the other hand, a materialhaving a low refractive index has a tendency to transmit EUV light.Pairing these two type materials together provides a resonantreflectivity. In some embodiments, the reflective multilayer structure110 includes alternatively stacked layers of molybdenum (Mo) and silicon(Si). In some embodiments, the reflective multilayer structure 110includes alternatively stacked Mo and Si layers with Si being in the toplayer. In some embodiments, a molybdenum layer is in direct contact withthe front surface of the substrate 102. In other some embodiments, asilicon layer is in direct contact with the front surface of thesubstrate 102. Alternatively, the reflective multilayer structure 110includes alternatively stacked layers of Mo and beryllium (Be).

The thickness of each layer in the reflective multilayer structure 110depends on the EUV wavelength and the incident angle. The thickness ofalternating layers in the reflective multilayer structure 110 is tunedto maximize the constructive interference of the EUV light reflected ateach interface and to minimize the overall absorption of the EUV light.In some embodiments, the reflective multilayer structure 110 has athickness ranging from about 250 nm to about 350 nm. In someembodiments, the reflective multilayer structure 110 includes forty (40)pairs of alternating layers of Mo and Si. Each Mo/Si pair has athickness of about 5 nm to about 7 nm, with a total thickness of about300 nm.

In some embodiments, each layer in the reflective multilayer structure110 is deposited over the substrate 102 and underlying layer using ionbeam deposition (IBD) or DC magnetron sputtering. The deposition methodused helps to ensure the thickness uniformity of the reflectivemultilayer structure 110 is better than about 0.85 across the substrate102.

The adhesion layer 112 is disposed over the reflective multilayerstructure 110. In some embodiments, the adhesion layer 112 is in directcontact with the topmost surface of the reflective multilayer structure110. The adhesion layer 112 provides good adhesion for the capping layer114 subsequently formed thereon. The adhesion layer 112, thus helps toprevent or reduce self-crystallization of the capping layer 114 duringthe deposition of the material that provides the capping layer 114,rendering the capping layer 114 formed there on amorphous orsemi-crystalline. The adhesion layer 112 also acts as a barrier layer,preventing the intermixing of the metal in the capping layer 114 andsilicon in top silicon layer of the reflective multilayer structure 110during the use of the EUV mask 100. As a result, the stability of theEUV mask 100 is improved.

In some embodiments, the adhesion layer 112 includes or is made of adielectric material such as, for example, silicon oxide, siliconoxynitride, silicon nitride, or a combination thereof. In someembodiments, the adhesion layer 112 is formed using a deposition processsuch as, for example, CVD, PECVD, PVD, or atomic layer deposition (ALD).In some embodiments, the adhesion layer 112 is formed by conversion of asurface portion of the Si top layer in the reflective multilayerstructure 110 using oxidation and/or nitridation. In some embodiments,the adhesion layer 112 includes silicon oxide and is formed byconversion of a surface portion of the Si top layer using a thermaloxidation process or a plasma oxidation process.

The thickness of the adhesion layer 112 is controlled to ensure that acontinuous coverage of the adhesion layer 112 on the underlyingreflective multilayer structure 110 is obtained. In some embodiment, theadhesion layer 112 has a thickness raging from about 1 nm to about 3 nm.If the thickness of the adhesion layer 112 is too small, a continuouscoverage of the adhesion layer 112 cannot be obtained, in someinstances. In such case, the capping layer material can still bedeposited directly on the surface of the reflective multilayer structure110, and the crystallization of the capping layer material and/orintermixing of the capping layer material and silicon can occur inregions where the reflective multilayer structure 110 not covered by theadhesion layer 112. The crystallization of the capping layer materialand/or intermixing of the capping layer material and silicon reduce theuniformity of the capping layer 114, which adversely affects the qualityof the EUV mask 100. On the other hand, if the thickness of the adhesionlayer 112 is too large, a great decrease in the reflectivity of thereflective multilayer structure 110 occurs, which leads to criticaldimension (CD) errors in the lithography processes, in some instances.

The capping layer 114 is disposed over the adhesion layer 112. In someembodiments, the capping layer 114 is in direct contact with a topsurface of the adhesion layer 112. The capping layer 114 helps toprevent oxidation of the top Si layer in the reflective multilayerstructure 110 during the fabrication and use of the EUV mask 100. In thepresent disclosure, because the capping layer 114 is deposited on theadhesion layer 112 which provides stronger bonding to the capping layer114 compared to instances where the capping layer 114 is directlydeposited onto the reflective multilayer structure 110, the presence ofthe adhesion layer 112 helps to prevent self-crystallization of thecapping layer material, which results in massive grain boundaries anddefect areas. The resulting capping layer 114 has an amorphous or asemi-crystalline structure. The capping layer 114, thus, has a smoothersurface than the crystalline counterpart, which helps to improve theuniformity of the capping layer 114.

In some embodiments, the capping layer 114 includes a material thatresists oxidation and corrosion, and has a low chemical reactivity withcommon atmospheric gas species such as oxygen, nitrogen, and watervapor. In some embodiments, the capping layer 114 includes a transitionmetal such as, for example, Ru, iridium (Ir), Rhodium (Rh), platinum(Pt), palladium (Pd), osmium (Os), rhenium (Re), vanadium (V), Tantalum(Ta), hafnium (Hf), tungsten (W), molybdenum (Mo), zirconium (Zr),manganese (Mn), or technetium (Tc).

In some embodiments, the capping layer 114 further includes one or moredopants having a carbon solubility less than a carbon solubility of thematerial providing the capping layer 114. In some embodiments, thedopant has a carbon solubility less than that of the transition metalproviding the capping layer 114. Exemplary dopants include, but are notlimited to, niobium (Nb), titanium (Ti), zirconium (Zr), yttrium (Y),boron (B), and phosphorus (P). Introducing dopants into the cappinglayer 114 helps to prevent the accumulation of carbon in the cappinglayer 114 during the use of the EUV mask 100, which improves the longterm stability of the EUV mask 100. The amount of the dopants in thecapping layer 114 is controlled to prevent the formation ofintermetallic compounds of two metals, which reduces uniformity of thecapping layer 114. In some embodiments, the ratio of Ru and dopantelement is controlled in a range from about 1:0 to about 2:1. In someembodiments, the concentration of dopants in the capping layer 114 isless than about 50 atomic percent (at. %). Because dopant elementsnormally have a density less than the density of Ru, if dopants areintroduced into the capping layer 114, the density of the resultingcapping layer 114 is less than the bulk density of Ru (e.g., about 12.45g/cm³).

In some embodiments, the capping layer 114 is formed using a depositionprocess such as, for example, IBD, CVD, PVD, or ALD. In someembodiments, the dopants are introduced into the capping layer 114 byion implantation after the capping layer 114 is formed. In someembodiments, the dopants are co-deposited with the material providingthe capping layer 114.

The absorber layer 116 is disposed over the capping layer 114. In someembodiments, the absorber layer 116 is in direct contact with a topsurface of the capping layer 114. The absorber layer 116 includes amaterial having a high absorption coefficient in EUV wavelengths. Insome embodiments, the absorber layer 116 includes a material having ahigh absorption coefficient at 13.5 nm wavelength. In some embodiments,the absorber layer 116 includes or is made of chromium (Cr), chromiumoxide (CrO), titanium nitride (TiN), tantalum nitride (TaN), tantalum(Ta), titanium (Ti), Mo, aluminum-copper (Al—Cu), palladium (Pd),tantalum boron nitride (TaBN), tantalum boron oxide (TaBO), aluminumoxide (Al₂O₃), silver oxide (Ag₂O), or a combination thereof. In someembodiments, the absorber layer 116 has a single layer structure. Insome other embodiments, the absorber layer 116 has a multilayerstructure. In some embodiments, the absorber layer 116 is formed by adeposition process such as, for example, CVD, PECVD, PVD, or ALD.

The anti-reflection layer 118 is disposed over the absorber layer 116.In some embodiments, the anti-reflection layer 118 is in direct contactwith a top surface of the absorber layer 116. The anti-reflection layer118 reduces reflection of light from underlying layers during thelithography patterning of the photoresist layer 140 and thus helps toincrease the precision of patterns formed in the photoresist layer 140.In some embodiments, the anti-reflection layer 118 includes a metaloxide such as tantalum oxide (TaO) or tantalum boron oxide (TaBO), ametal such as Ru, Ti, Niobium (Nb), Zirconium (Zr), hafnium (Hf),platinum (Pt) or iridium (Ir). In some embodiments, the anti-reflectionlayer 118 is formed using a deposition process such as, for example,CVD, PECVD, or PVD.

The hard mask layer 130 is disposed over the anti-reflection layer 118.In some embodiments, the hard mask layer 130 is in direct contact withthe anti-reflection layer 118. In some embodiments, the hard mask layer130 includes a dielectric oxide such as silicon dioxide or a dielectricnitride such as silicon nitride. In some embodiments, the hard masklayer 130 is formed using a deposition process such as, for example,CVD, PECVD, or PVD.

The photoresist layer 140 is disposed over the hard mask layer 130. Thephotoresist layer 140 includes a photosensitive material operable to bepatterned by radiation. In some embodiments, the photoresist layer 140includes a positive-tone photoresist material, a negative-tonephotoresist material or a hybrid-tone photoresist material. In someembodiments, the photoresist layer 140 is applied to the surface of thehard mask layer 130 by a deposition process, such as spin coating.

Referring to FIGS. 2 and 3B, the method 200 proceeds to operation 204,in which the photoresist layer 140 is patterned to form a patternedphotoresist layer 140P, in accordance with some embodiments. Thephotoresist layer 140 is patterned by first subjecting the photoresistlayer 140 to a pattern of irradiation. Next, the exposed or unexposedportions of the photoresist layer 140 are removed depending on whether apositive-tone or negative-tone resist is used in the photoresist layer140 with a resist developer, thereby forming the patterned photoresistlayer 140P having a pattern of openings 142 formed therein. The openings142 expose portions of the hard mask layer 130. The openings 142 arelocated in the pattern region 100A and correspond to locations where thepattern of openings 122 are present in the EUV mask 100 (FIG. 1 ).

Referring to FIGS. 2 and 3C, the method 200 proceeds to operation 206,in which the hard mask layer 130 is etched using the patternedphotoresist layer 140P as an etch mask to form a patterned hard masklayer 130P, in accordance with some embodiments. Portions of the hardmask layer 130 that are exposed by the openings 142 are etched to formopenings 144 extending through the hard mask layer 130. The openings 144expose portions of the anti-reflection layer 118. In some embodiments,the hard mask layer 130 is etched using an anisotropic etch. In someembodiments, the anisotropic etch is a dry etch such as, for example,reactive ion etch (RIE), a wet etch, or a combination thereof. The etchremoves the material providing the hard mask layer 130 selective to thematerial providing the anti-reflection layer 118. The remaining portionsof the hard mask layer 130 constitute the patterned hard mask layer130P. If not completely consumed during the etching of the hard masklayer 130, after etching the hard mask layer 130, the patternedphotoresist layer 140P is removed from the surface of the patterned hardmask layer 130P, for example, using wet stripping or plasma ashing.

Referring to FIGS. 2 and 3D, the method 200 proceeds to operation 208,in which the anti-reflection layer 118 and the absorber layer 116 areetched using the patterned hard mask layer 130P as an etch mask to forma patterned anti-reflection layer 118P and a patterned absorber layer116P, respectively, in accordance with some embodiments. Portions of theanti-reflection layer 118 that are exposed by the openings 144 andportions of the absorber layer 116 that underlie the exposed portions ofthe anti-reflection layer 118 are etched to form openings 122 extendingthrough the anti-reflection layer 118 and the absorber layer 116. Theopenings 122 are in the pattern region 100A of the EUV mask 100 andcorrespond to circuit patterns formed on a semiconductor wafer. Theopenings 122 expose portions of the capping layer 114. In someembodiments, the anti-reflection layer 118 and the absorber layer 116are etched using a single anisotropic etching process. In someembodiments, the anisotropic etch is a dry etch such as, for example,ME, a wet etch, or a combination thereof that removes the materialproviding the anti-reflection layer 118 and the material providing theabsorber layer 116 selective to the material providing the capping layer114. In some embodiments, the anti-reflection layer 118 and the absorberlayer 116 are etched using two different anisotropic etching processes.Each anisotropic etch can be a dry etch such as, for example, RIE, a wetetch, or a combination thereof. The first etch removes the materialproviding the anti-reflection layer 118 selective to the materialproviding the absorber layer 116, and the second etch removes thematerial providing the absorber layer 116 selective to the materialproviding the capping layer 114. The remaining portions of theanti-reflection layer 118 constitute the patterned anti-reflection layer118P. The remaining portions of the absorber layer 116 constitute thepatterned absorber layer 116P.

Referring to FIGS. 2 and 3E, the method 200 proceeds to operation 210,in which the patterned hard mask layer 130P is removed, in accordancewith some embodiments. In some embodiments, the patterned hard masklayer 130P is removed from the surfaces of the patterned anti-reflectionlayer 118P, for example, using oxygen plasma or a wet etch.

Referring to FIGS. 2 and 3F, the method 200 proceeds to operation 212,in which a photoresist layer 150 is formed on the capping layer 114 andthe patterned anti-reflection layer 118P, in accordance with someembodiments. The photoresist layer 150 fills the openings 122 in thepattern region 100A of the substrate 102. In some embodiments, thephotoresist layer 150 includes a positive-tone photoresist material, anegative-tone photoresist material or a hybrid-tone photoresistmaterial. In some embodiments, the photoresist layer 150 includes a samematerial as the photoresist layer 140 described above in FIG. 3A. Insome embodiments, the photoresist layer 150 includes a differentmaterial from the photoresist layer 140. In some embodiments, thephotoresist layer 150 is formed, for example, by spin coating.

Referring to FIGS. 2 and 3G, the method 200 proceeds to operation 214,in which the photoresist layer 150 is patterned to form a patternedphotoresist layer 150P containing a pattern of openings 152 therein, inaccordance with some embodiments. The openings 152 expose portions ofthe anti-reflection layer 118P where trenches 124 in the peripheralregion 100B of the EUV mask 100 are to be formed. In some embodiments,the photoresist layer 150 is patterned by exposing the photoresist layer150 to a pattern of radiation, and removing the exposed or unexposedportions of the photoresist layer 150 using a resist developer dependingon whether a positive or negative resist is used. The remaining portionsof the photoresist layer 150 constitute the patterned photoresist layer150P.

Referring to FIGS. 2 and 3H, the method 200 proceeds to operation 216,in which the patterned anti-reflection layer 118P, the patternedabsorber layer 116P, the capping layer 114, the adhesion layer 112, andthe reflective multilayer structure 110 are etched using the patternedphotoresist layer 150P as an etch mask to form trenches 124 in theperipheral region 100B of the substrate 102, in accordance with someembodiments. In some embodiments, the trenches 124 extend into thereflective multilayer structure 110. In some embodiments, the trenches124 expose the surface of the substrate 102.

In some embodiments, the patterned anti-reflection layer 118P, thepatterned absorber layer 116P, the capping layer 114, the adhesion layer112, and the reflective multilayer structure 110 are etched using asingle anisotropic etching process. The anisotropic etch can be a dryetch such as, for example, RIE, a wet etch, or a combination thereofthat removes materials of respective patterned anti-reflection layer118P, the patterned absorber layer 116P, the capping layer 114, theadhesion layer 112, and the reflective multilayer structure 110selective to the material providing the substrate 102. In someembodiments, the patterned anti-reflection layer 118P, the patternedabsorber layer 116P, the capping layer 114, the adhesion layer 112, andthe reflective multilayer structure 110 are etched using multipledistinct anisotropic etching processes. Each anisotropic etch can be adry etch such as, for example, RIE, a wet etch, or a combinationthereof.

After formation of the trenches 124, the patterned photoresist layer150P is removed, for example, by wet stripping or plasma ashing. Theremoval of the patterned photoresist layer 150P re-expose the surface ofthe substrate 102 in the openings 122.

Many variations and/or modifications can be made to embodiments of thedisclosure. In some other embodiments, the reflective multilayerstructure 110 is replaced with another reflective structure that has asingle-layer structure.

One aspect of this description relates to a photolithography mask. Thephotolithography mask includes a substrate, a reflective multilayerstructure over the substrate, an adhesion layer over the reflectivemultilayer structure, a capping layer over the adhesion layer, and apatterned absorber layer over the capping layer. The capping layerincludes a non-crystalline conductive material.

Another aspect of this description relates to relates to aphotolithography mask. The photolithography mask includes a substrate, areflective multilayer structure over the substrate, an adhesion layerover the reflective multilayer structure, a capping layer over theadhesion layer, and a patterned absorber layer over the capping layer.The adhesion layer includes a dielectric material, and the capping layerincludes an amorphous conductive material.

Still another aspect of this description relates to a method of forminga photolithography mask. The method includes depositing a reflectivemultilayer structure over a substrate. The method further includesforming an adhesion layer over the reflective multilayer structure. Themethod further includes depositing a capping layer over the adhesionlayer. The capping layer includes an amorphous conductive material. Themethod further includes depositing an absorber layer over the cappinglayer. The method further includes etching the absorber layer to form aplurality of openings exposing a surface of the capping layer.

The foregoing outlines features of several embodiments so that thoseskilled in the art may better understand the aspects of the presentdisclosure. Those skilled in the art should appreciate that they mayreadily use the present disclosure as a basis for designing or modifyingother processes and structures for carrying out the same purposes and/orachieving the same advantages of the embodiments introduced herein.Those skilled in the art should also realize that such equivalentconstructions do not depart from the spirit and scope of the presentdisclosure, and that they may make various changes, substitutions, andalterations herein without departing from the spirit and scope of thepresent disclosure.

What is claimed is:
 1. A photolithography mask, comprising: a substrate;a reflective multilayer structure over the substrate; an adhesion layerin direct contact with a topmost surface of the reflective multilayerstructure; a capping layer over the adhesion layer; and a patternedabsorber layer over the capping layer.
 2. The photolithography mask ofclaim 1, wherein the adhesion layer comprises a dielectric material. 3.The photolithography mask of claim 2, wherein the dielectric materialcomprises silicon dioxide, silicon nitride or silicon oxynitride.
 4. Thephotolithography mask of claim 1, wherein the capping layer comprises anon-crystalline conductive material.
 5. The photolithography mask ofclaim 4, wherein the non-crystalline conductive material comprises atransition metal selected from ruthenium, iridium, rhodium, platinum,palladium, osmium, rhenium, vanadium, tantalum, hafnium, tungsten,molybdenum, zirconium, manganese and technetium.
 6. A method for forminga photolithography mask, comprising: forming a reflective multilayerstructure over a first side of a substrate; forming an adhesion layerover the reflective multilayer structure; depositing a capping layerover the adhesion layer; depositing an absorber layer over the cappinglayer; and etching the absorber layer to form a plurality of openingsexposing a surface of the capping layer.
 7. The method of claim 6,wherein the adhesion layer comprises a dielectric material selected fromthe group consisting of silicon dioxide, silicon nitride and siliconoxynitride.
 8. The method of claim 7, wherein forming the adhesion layercomprises depositing the dielectric material over the reflectivemultilayer structure.
 9. The method of claim 7, wherein forming theadhesion layer comprises converting a surface portion of a topmost layerin the reflective multilayer structure using oxidation and/ornitridation to form the dielectric material.
 10. The method of claim 6,wherein the capping layer comprises an amorphous conductive material.11. The method of claim 10, wherein the capping layer comprisesamorphous ruthenium.
 12. The method of claim 10, wherein the cappinglayer further comprises one or more dopants selected from the groupconsisting of niobium, titanium, zirconium, yttrium, boron andphosphorus.
 13. The method of claim 12, wherein depositing the cappinglayer comprising co-depositing the conductive material and the one ormore dopants using a deposition process.
 14. The method of claim 8,further comprising depositing a conductive layer on a second side of thesubstrate opposite the first side.
 15. A lithography patterning processcomprising transferring a pattern from a photolithography mask to asemiconductor wafer, wherein the photolithography mask comprises: asubstrate; a reflective multilayer structure over the substrate; anadhesion layer in direct contact with a topmost surface of thereflective multilayer structure; a capping layer over the adhesionlayer; and a patterned absorber layer over the capping layer.
 16. Thelithography patterning process of claim 15, wherein the adhesion layercomprises a dielectric material, and the capping layer comprises anon-crystalline conductive material.
 17. The lithography patterningprocess of claim 15, wherein the adhesion layer comprises silicondioxide, silicon nitride or silicon oxynitride.
 18. The lithographypatterning process of claim 15, wherein the capping layer comprises atransition metal selected from ruthenium, iridium, Rhodium, platinum,palladium, osmium, rhenium, vanadium, tantalum, hafnium, tungsten,molybdenum, zirconium, manganese and technetium.
 19. The lithographypatterning process of claim 15, wherein the capping layer furthercomprises one or more dopants selected from the group consisting ofniobium, titanium, zirconium, yttrium, boron and phosphorus (P).
 20. Thelithography patterning process of claim 19, wherein a concentration ofthe one or more dopants in the capping layer is less than about 50atomic percent.